Based on the teachings in Chapter 20, why is a Guru's grace considered essential for understanding profound scriptures like the Upanishads?

Chapter 20 powerfully argues that a Guru's grace is indispensable for grasping deep spiritual knowledge. It explains that the Upanishads, which hold the essence of the Vedas, are incredibly difficult to comprehend without the grace of 'Hari (God) and Guru.' The text explicitly states that a scholar who arrogantly believes they can understand these texts through their own intellectual efforts will fail, as the 'hidden truth does not come to hand.' Conversely, for a humble devotee who is attached to the Guru's feet, there is no difficulty at all, and the hidden meanings of the scriptures open up automatically. This illustrates that true understanding is a matter of grace and humility, not just scholarship.